Apparatuses, so-called refrigeration cycle apparatuses, utilizing a refrigeration cycle of a refrigerant, i.e., compressing, radiating, expanding, and vaporizing, are used for a variety of applications, such as air conditioners and water heaters. As an expander-compressor unit used for such refrigeration cycle apparatuses, there can be mentioned a unit designed for improving efficiency of the refrigeration cycle by coupling, with a shaft, an expansion mechanism that converts the expansion energy generated during the expansion of refrigerant under reduced pressure into mechanical energy and recovers the resulting mechanical energy, and a compression mechanism that compresses the refrigerant, and by supplying the mechanical energy recovered by the expansion mechanism to the compression mechanism (JP 62(1987)-77562 A).
Since the compression mechanism adiabatically compresses the refrigerant, the temperatures of the components of the compression mechanism rises in accordance with the temperature of the refrigerant. On the other hand, the temperatures of the components of the expansion mechanism lower in accordance with the temperature of the refrigerant because the refrigerant cooled with a radiator flows into the expansion mechanism and is expanded adiabatically. Thus, mere integration of the compression mechanism and the expansion mechanism as described in JP 62 (1987)-77562 A unfavorably allows the heat on the compression mechanism side to transfer to the expansion mechanism side. Such a heat transfer means that unintended heating of the refrigerant will occur at the expansion mechanism as well as that unintended cooling of the refrigerant will occur at the compression mechanism, leading to a reduced efficiency of the refrigeration cycle.
In order to solve this problem, it has been a proposal to provide a heat insulating member between the compression mechanism and the expansion mechanism so as to block the heat transfer from the compression mechanism to the expansion mechanism (JP 2001-165040 A). Furthermore, it has been proposed to dispose, as shown in FIG. 10, a compression mechanism 102, a motor 103, and an expansion mechanism 104 in a closed casing 101 in this order from the bottom, while providing a heat insulating member 105 on a surface of the expansion mechanism 104 so as to block the heat transfer from the surrounding refrigerant (JP 3674625 B).